* {
    box-sizing: border-box;
}

html {
    height: 100%;
}

body {
    height: 100%;
}
header{
    font-size: 30px;
    text-align: center;
}
ul>li{
    list-style: none;
}
ul>li>img{
    height: 50px;
    width: 50px;
    border-radius: 50%;
}

.active{
    background-color: lightblue;
}
footer {
    width: 100%;
    position: fixed;
    bottom: 0;
    left: 0;
    height: 60px;
    line-height: 60px;
    border-top: 1px solid gray;
}

footer span {
    float: left;
    width: 33.3%;
    text-align: center;
    font-size: 25px;
    border-right: 1px solid gray;
}
footer span:nth-child(3){
    border-right: none;
}